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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 14th Jan 2015, 16:28
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Originally Posted by A0283
I have not had time to think about what kind of aerodynamic forces would shape this 'hand'.
For my money, your second point on "hydrodymanic forces" is a good avenue of inquiry.
Such a twisting might be the result of a rotating body not hitting the water's surface in a more or less "flat" attitude (as did AF 447) but rather in a more or less "tilted" attitude.
It might not need to rotating to get a tear like that if it has sufficient ground speed and tilt, depending on the vertical velocity at impact as compared to lateral / horizontal velocity.
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Old 14th Jan 2015, 16:40
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Feedback to Lonewolf

For my money, your second point on "hydrodymanic forces" is a good avenue of inquiry. Such a twisting might be the result of a rotating body not hitting the surface in a more or less "flat" attitude (as did AF 447) but rather in a more or less "tilted" attitude - and it might not need to be rotating if it has sufficient ground speed vector to create torsion/shear.
Lonewolf, I started out with the aerodynamic. Then considered the hydrodynamic. But today officials stated that tail and FDR/CVR were 800 m apart, and tail and main fuselage plus wings 2,000 m. That increased the probability on the side of the aerodynamic. Also, because the vertical stabilizer still looked pretty smooth.

The damage to the lower side of the rudder area, that looks a bit like that on (high speed) AF447. Which puts another grain of salt on the aerodyn scale. Don't you think?

Last edited by A0283; 14th Jan 2015 at 16:52. Reason: add ?
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Old 14th Jan 2015, 16:41
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Surely how it hit the water, and what caused the damage seen is really of little matter.

It may or may not indicate if there was any control at the time it hit the water, but again, that won't help find the cause.

What is needed is the reason that caused the loss of control (not pointing to pilot involvement or not) at some 30k feet above the damage being looked at.

Maybe this is why they are not too worried about the "hacking up" of the wreckage?
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Old 14th Jan 2015, 16:42
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Having done a high-altitude stalling module recently, I thought it was of great benefit despite the caveat that the aerodynamic simulation might not be exact.

It showed:

a) You had to agressively reduce the AoA by pitching down to a far greater degree than in any other flight phase.

b) The engines were next to useless, given spool-up times and the thrust generated near the aircraft ceiling, so it was more a glider-style recovery.

c) You were going to lose a LOT of altitude, no matter what.

d) If you tried to level out too early, before getting to c), it was quite possible to stall again.

I would argue that the fidelity of the simulator was unimportant in getting those basic principles across. After all, every LoC / jet upset is different, especially if it has been in part caused by something malfunctioning, be it software, hardware or wetware.
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Old 14th Jan 2015, 16:48
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@A0283:
I see your points. Just a thought: once things fell apart, the movement of the water and "how long a given bit floats" may offer sufficient explanation for how the dispersal came about. Or not.
You are more likely right in your estimates, as you've examined it in more detail.
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Old 14th Jan 2015, 17:05
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That is a great deal more intact than I thought it would be. I expected component parts.
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Old 14th Jan 2015, 17:19
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No sign yet of front part of fuselage, ie cockpit?
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Old 14th Jan 2015, 17:21
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Let's face it... hydrodynamic forces would be capable of anything
imaginable and unimaginable entering water at speeds from 100 kts
upwards. Including twisting and if the tail struck first, tearing it off.
lets see
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Old 14th Jan 2015, 17:21
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To Msunduzi

Surely how it hit the water, and what caused the damage seen is really of little matter.
It may or may not indicate if there was any control at the time it hit the water, but again, that won't help find the cause.
What is needed is the reason that caused the loss of control (not pointing to pilot involvement or not) at some 30k feet above the damage being looked at.
Maybe this is why they are not too worried about the "hacking up" of the wreckage?
My impression is that 'losing control at high altitude' would happen more often (probability wise and statistically), than things getting 'out of control' ( either by weather events (that's one reason why we have pilots who can put things right), or SA loss leading to a flip like the 747 years ago (where the pilot provided both cause and solution, albeit after a significant drop) ). If that is so, then you would have to divide the flight path in altitude steps, call it a 'ladder'. And ask for each step of the ladder what happens, and what the pilots' options are. Like posters do in the interesting stall discussions here. And that also includes the final splash. The whole plane hitting the water or large separate sections ... that points to different possible causes. Which you test by going up the ladder again. Both top and bottom of the ladder are relevant for 'solving' this accident.

On hacking up. Nobody knows what the cause was. Real hacking up would not start until after reading and analyzing the recorders and the investigation being further along the line. The only reason for hacking up now would be transportation requirements (bridges, roadwidth ..etc ... the diameter of the fuselage is 4.14 m ... one lane on western highways is something like 3 m...isn't it?)
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Old 14th Jan 2015, 17:47
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Maybe this is why they are not too worried about the "hacking up" of the wreckage?
I tend to agree. Before the tail was recovered, there was an official statement that the rescuers first priority was finding the casualties, the second was the black boxes.

The main interest in the wreckage, as reported, was about the position of the control surfaces (or "tail flaps" as it was reported) which could give valuable information about the airplane's last flying moments. Based on that information, the interesting pieces would IMHO be the actuators and the THS jackscrew.

Presumably the rescuers also took enough underwater photos and videos to enable them to establish the pre-recovery condition of the wreckage. I'd assume that to be standard practice in this kind of salvage jobs.
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Old 14th Jan 2015, 17:48
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To Lonewolf ...

@A0283: I see your points. Just a thought: once things fell apart, the movement of the water and "how long a given bit floats" may offer sufficient explanation for how the dispersal came about. Or not. You are more likely right in your estimates, as you've examined it in more detail.
At first thought. There might be two 'theoretical reasons' that could explain the 2,000 m. First floating, and second forward speed. But both start with hitting the water and losing the THS and the bottom of the tail with the APU.

On the first, floating. So you have an open tube ... which if it fills, will fill quickly ... if not, the plane might be weighed nose down and keep the open end up for a while (until the swell flows in) and might float around a bit ... at the 1-2 knots published current that distance would take roughly 30 minutes to 60 minutes.

On the second. The forward speed would combine losing the tail followed by skimming over the surface like a flat stone. At say 60-120 knots that would be roughly 2,000 m in roughly 0.6-1.2 min. The impression is that the plane went up and down quite vertical (not far from LKP) and pretty fast. So, that seems to be less probable.... In spite of the fact that the lower aft section may still have been attached (as mentioned, the aft top panel stayed connected to the tail/rudder section).

What it does not explain is the apparent stripping of most interior components..... Which gives a bit more probability on the side of a higher speed and above break up. Also, skimming has lower probability, when reviewing earlier widebody waterlandings.

Theory and practice can be quite different of course. But it gives some idea I guess. And no more than 'some' idea ... at this stage and with the publicly available information.

Last edited by A0283; 14th Jan 2015 at 17:53. Reason: Add ")"
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Old 14th Jan 2015, 18:29
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the wreckage looks very much less fragmented then i/we were expecting

reminds me of 2 tridents that went down with little or no forward speed

PI and ZT both had wreckage/fuselage compacting that looked somewhat like this with wings attached
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Old 14th Jan 2015, 18:46
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BEANCOUNTERS...

someone mentioned clearing the BEANCOUNTERS from responsibility, blaming instead a lack of required standards

SO


Back in the beginning, there were no standards and we learned the hard way what had to be done to keep things safe and assure passengers there was as good a chance to get from A to B on an airliner as on a train, ship, car, or horse.

And they did it.

And then the regulators codified many of those same things.

BUT THEN came the cheapos. IF THE FAA or over seas version hasn't mandated it, then WE DON'T HAVE TO DO IT and can save money.

THE OLD GUYS shook their heads...they knew better. We are learning the same things over and over again that we knew 40 years ago.

all at the cost of passengers and crew.


So it is beancounters, because they have an excuse, an ENABLER in local regs that aren't as tight as a drum.
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Old 14th Jan 2015, 18:48
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Given the remarkable condition of the fuselage, an attempted but unsuccessful "controlled" ditch in gale conditions?
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Old 14th Jan 2015, 18:55
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There has been some discussion on hydrodynamic forces as cause for apparent damage.

By way of a reminder I would say that my understanding of hydrodynamic force is the forces acting in fluids in motion and not objects that impact fluids such as water. Accordingly unless someone pulls a stunt such as flying into Niagara Falls at their full fury then the question of hydrodynamic force does not really come into play.
The damage sustained to an aircraft impacting against any surface is caused by the dynamic force of the travelling aircraft and not by movement of the surface or depth of the water.
In this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations.
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Old 14th Jan 2015, 19:35
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in this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations.
I just would not have expected the remainder of the airframe to survive anything like to the extent it has. It appears borderline surviveable, and the fuselage (what is visible) still looks circular.
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Old 14th Jan 2015, 19:36
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Boomntown - doubt it. You would need a failure that left the pilots flying, but all radios disabled.
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Old 14th Jan 2015, 19:42
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A bean counters job is to count beans, not dictate morality and standards. Their jobs is to the best of their ability to come up with ways to legally save money. Failure to do that is not doing their jobs.

Its other peoples jobs to evaluate those recommendations and consequences of, and they should do that to the best of their abilities.

If some thing is serious enough, as a society we codify it.
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Old 14th Jan 2015, 19:43
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Wasn't there a theory going around that the inflated rear exit slide was at first attatched to the severed rear section causing it to float away while the main body sank immediately. The slide subsequently detatching in the swell so that the tail section sank some distance away?
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Old 14th Jan 2015, 19:52
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QUOTE:in this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations.END QUOTE



Can anyone tell me if there has ever been a failure of the empenage in ANY Airbus Product? ;-)
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